That’s a trickier question than you think it is. NFPA211, the standard for our industry, says that all flues should be inspected annually and cleaned* as needed. That’s a great idea and fantastic job security for chimney sweeps, but not always realistic for everyone. What if you never use your fireplace? I’ve had more than a few customers who use their fireplace only once or twice a year. It’s simply not necessary to sweep that flue with such little use. I like to give my customers two good rules of thumb for maintenance:

  1. After every cord of wood. If you order a cord and you’re getting down to the last couple of logs, it’s probably time to have it swept.
  2. If you use a fireplace twice a week or more during the winter, it should be swept every year. Excessive use—every day, all day—may even require more than one sweep a year. If you’re more of a weekend warrior—once a week or less—then I would suggest a sweep every two years. The caveat to this would be what I call “binge burning”. Some folks tell me they only use the fireplace once a week or less, then I find out they’re burning it from early morning until late at night. Binge burning can equal several evenings’ fire in one day. If this is your habit, you should have that swept yearly.

Wood stoves and inserts should also be swept according to use. Oil heating flues can depend on the efficiency of the unit, but having them swept every couple of years is usually a good idea. Gas heating flues do not really produce a soot that needs sweeping, but they should be inspected regularly. These rules of thumb also apply to folks who just use Duraflames or other manufactured logs. They may be ‘cleaner’ burning in your fireplace, but they put just as much soot inside a flue as a wood log.

Where I agree with NFPA211 is on the inspection side of things. Things can go wrong inside a chimney even when they’re not being used. Mortar can deteriorate, liners can crack, and bricks can fall. Regular chimney inspections should be a part of your home maintenance routine to make sure any repair issues that come up can be caught early before they become a more serious problem.

*Many sweeps dislike their wording of “cleaned”. No chimney sweep cleans anything, we sweep things. When we are done, your fireplace and flue will not be spotlessly clean. You can sweep your kitchen floor, but you wouldn’t eat off of it afterwards, would you? That’s the difference between ‘clean’ and ‘sweep’.